The production of phenol by partial oxidation of benzene using nitrous oxide over a variety of catalysts ranging from vanadium pentoxide on silica to zeolites, e.g. ZSM-5 and ZSM-11 zeolite catalysts, at elevated temperatures, e.g. 300.degree. to 450.degree. C., has been disclosed. When benzene is replaced by a benzene derivative such a chlorobenzene, fluorobenzene, toluene or ethylbenzene, the corresponding substituted phenol can be produced. When phenol itself is the substituted benzene, the reaction products include dihydroxybenzenes such as hydroquinone, resorcinol and catechol. Phenol and its derivatives, for example, dihydric phenols, chlorophenols, nitrophenols, cresols and other hydroxyl-containing aromatic compounds are valuable products that find wide applications in industry. The most common commodity chemical of this class is phenol, which is used mainly in production of phenolic resins, caprolactam, nitrophenols and chlorophenols, etc. For decades, the researchers have searched for simple and efficient methods of syntheses of phenol and its derivatives. Iwamoto et al. in J. Physical Chemistry (ACS), Vol. 87, No. 6, (1983) p. 903-905 reported that single-step hydroxylation of aromatic compounds could be effected using nitrous oxide as an oxidant in the presence of traditional catalysts for partial oxidation, e.g. supported oxides of vanadium, molybdenum and tungsten. Iwamoto conducted the reaction at 550.degree. C. with benzene conversion of 10% and selectivity towards phenol of 72%. Though these results were far superior to all previous achievements, still they turned out to be insufficient for practical use of the process, which dictated the need for search of more efficient systems.
The use of new type of catalysts, e.g. high silica aluminosilocates with zeolite structure, for the hydroxylation of benzene was reported by Suzuki et al. in the Chemical Society of Japan's Chemistry Letters, (1988) p. 953-956; by Gubelmann et al. in U.S. Pat. No. 5,055,623; and by Kharitonov et al., in U.S. Pat. No. 5,110,995. In the presence of such zeolite catalysts the hydroxylation of benzene and other aromatic compounds occurs at 300.degree.-400.degree. C. with selectivity towards phenol of 90-100%. However, catalyst activity remains sufficiently inadequate for commercial practice of this technology.
Researchers continue to discover new ways to improve the process parameters and/or enhance the efficiency of zeolites, e.g. by introducing various kinds of catalyst pretreatment. In this regard, Zholobenko reported in Mendeleev Commun., (1993) No. 1, p. 28-29, a method for phenol production using zeolite catalyst that had been activated by high-temperature calcination in air. A drawback of this Zholobenko's method is that it does not provide any increase in catalyst activity at calcination temperatures below 700.degree. C. More particularly, because the activation effect is significant at higher temperatures (750.degree. C. and higher), Zholobenko's method is difficult to practically implement.